| Phenolic compounds are important chemical raw materials,it is toxic to the human body and the ecosystem.With the rapid development of industry,a large amount of phenol-containing wastewater is produced.It is necessary to find efficient methods to remove phenolic pollutants from wastewater.Persulfate(S2O82-)is a strong oxidant with advantages such as high solubility and stability.It can produce more oxidizing free radicals under the activated conditions of thermal,alkaline,transition metals and other types to better oxidize organic pollutants,which is widely used in wastewater treatment.Thermal activation is a highly efficient way to activate persulfate.In most cases,the reaction process can be speeded up by increasing temperature.The coupling of two or more activation techniques for persulfate can produce more free radicals and accelerate the reaction process.In this work,phenol,the most toxic phenolic compound,was selected as the target contaminant.The degradation efficiency of phenol in aqueous solution by using thermal activated sodium persulfate（PS）,alkaline thermal co-activated PS and Fe（Ⅱ）/thermal co-activated PS were investigated.1.The degradation effect of phenol in aqueous solution by using traditional thermal activated PS was investigated.The results showed that the removal rate of phenol was accelerated with the increase of reaction temperature（from 20℃to 60℃）and PS concentration（from 10 mmol/L to 50 mmol/L）.The degradation rate of phenol in the thermal activation system tended to be increased first,then decreased and then increased with the increase of pH（pH=3～13）.The active radicals were identified under different pH conditions,and it was determined that both sulfate radical（SO4-·）and hydroxyl adical（·OH）played important roles in phenol removal when pH rang was 5 to 11.When the pH was 13,the effect of SO4-·and·OH was weakened,and superoxide radical（O2-·）existed.What’s more,PS could be reduced by phenolic compounds,which could improve the removal rate of phenol.The degradation rate was inhibited by humic acid in aqueous solution.2.The degradation effect of phenol in aqueous solution by using alkaline thermal co-activated PS was investigated.The results showed that the degradation rate of phenol in the alkaline thermal co-activated PS system was higher than those in the single alkaline and the thermal activation system.After 80 min of reaction,the removal rate of phenol in the alkaline thermal co-activated PS system reached 98.59%.Compared to the single alkaline activation and the thermal activation system,the removal rate was increased by82.15%and 47.23%,respectively.The removal rate of phenol was accelerated with the increase of PS concentration（from 10 mmol/L to 50 mmol/L）,Na OH concentration（from0.1 mol/L to 1.5 mol/L）and reaction temperature（from 20℃to 60℃）.The degradation effect of phenol was also inhibited by the presence of humic acid.3.The degradation effect of phenol in aqueous solution by using Fe（Ⅱ）/thermal co-activated PS was investigated.The results showed that the optimum molar ratio of PS to Fe2+was 1:1,the degradation rate of phenol was increased with the increase of dosage.When the concentration of PS and Fe2+reached 5 mmol/L,reaction time was 90 min,the removal rate of phenol was 89.44%.A higher temperature or lower pH value would increase the removal rate.Radical inhibitor experiments and electron paramagnetic resonance（EPR）experiments confirmed that the main reactive oxygen species in this system are SO4-·and·OH.The addition of humic acid had a slight promoting effect on the removal of phenol.The results showed that the degradation rate of phenol in the Fe（Ⅱ）/thermal co-activated PS system was higher than that in the alkaline thermal co-activation system.After 40 min of reaction,the removal rate of phenol in the Fe（Ⅱ）/thermal co-activated PS system reached 94.57%.Compared to the alkaline thermal co-activated PS system,the removal rate was increased by 15.47%. |
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